Electronic i laboratory report

Procedure 1: Measurement of diode reverse leakage current Set-Up Configure a DC power supply to produce an output voltage of VSS = +10.0 Volts.. Procedure 2 Measurement of diode forward

Da Nang University of Science and Technology

EE231 Electronic I Laboratory Report

Team 1 : Đoàn Tuấn Sơn

Phan Văn Duy Vũ

Đặng Lê Trọng Anh

Lê Hoàng Tuấn Anh

Vũ 30% Tuấn Anh 10% Trọng Anh 20%

2 Design and

Vũ 30% Tuấn Anh 10% Trọng Anh 20%

Lab1: 2-Terminal Device Characteristics and Diode Characterization

Introduction: The objectives of this experiment are to learn methods for characterizing

2terminal devices, such as diodes, observe some fundamental trends in the

characteristics of various diode types, and to gain some familiarity with standard test bench instrumentation

Precautions: None of the devices used in this set of procedures are particularly static

sensitive; nevertheless, you should pay close attention to the circuit connections and to the polarity of the power supplies, diodes, and oscilloscope inputs

Procedure 1: Measurement of diode reverse leakage current

Set-Up Configure a DC power supply to produce an output voltage of VSS =

+10.0 Volts Verify this voltage with the bench DMM If the DC power supply has a current limiting ability, configure the power supply to limit the current to 100 mA Route the output of the DC power supply to your

breadboard using two squeeze hook test leads

For this next procedure you will measure the leakage current of four different diodes Each diode should be connected as shown in Fig E1.1

Use the following parts:

R1 = 1.0 M Ω 1% 1/4 W

D1 = 1N4007 and 1N5819

Use the solderless breadboard to connect the components, noting that each set of 5 vertically oriented holes constitutes a tie point The horizontal rows of holes are all internally connected into a single tie point; these are normally used for power supply distribution To attach test leads to the breadboard, you can use either the exposed end

of a component lead, or you can insert a small pin into the appropriate tie point and connect the squeeze hook or oscilloscope probe to the pin

Connect up only one diode at a time in the circuit of Fig E1.1, noting that the banded end of each diode is the cathode, which corresponds to the bar on the circuit symbol Connect the DC power supply across both R1 and D1 and then connect the DMM across only R1 using two pairs of squeeze hook test leads as shown above The DMM should read less than +10.0 V

Measurement-1: Measure the reverse leakage current for the 1N4007 and 1N5819

diodes Do this by using the DMM to measure the voltage across R1 and divide this voltage by R1 = 1.0 M Ω to obtain the current through R1, and therefore the current

through D1 Record your measurements and calculations in a table in your notebook

Question-1: Order these four diodes in rank, from smallest to largest reverse leakage

current Which diode would be the most suitable for charging up a capacitor and allowing the capacitor to keep its charge for the longest period of time?

1N5819, ~0.2V compared to ~0.7V for a pN junction diode, which means that the capacitor will be charged to a higher voltage and thus take a longer time to discharge

1N4007

R=1M Vd=0.5~0.7V

V=10V

Vr=9.72 Id=Vr/R=0.00000972

1N5819

R=1M Vd=0.2~0.3V

V=10V

Procedure 2 Measurement of diode forward turn-on voltage

Set-Up: In this procedure you will test each of the four diodes used in Procedure 1 at six

different current levels First note that the polarity of the diode is now reversed from that of the previous procedure The current levels will be set by R1 which will be set to one of six possible values To speed up this process, you may wish to insert all six resistors and all four diodes into the breadboard at once so that one end of each resistor connects to the anode of each diode The long, horizontal tie point strips on the solderless breadboard are quite convenient for this The proper resistor and diode can then be quickly selected by simply moving the power supply leads Use the bench DMM to measure the DC voltage across either the resistor or diode, as shown in Fig

E1.2

Connect the circuit for each diode and resistor pair as shown in Fig E1.2 using the following parts:

V1 = 0V,1V,2V,3V,4V,5V,6V,7V,8V,9V,10V,11V

D1 = 1N4007, 1N5819 and 1N4732

Measurement-2: For each of the two diodes (1N4007, 1N5819, 1N4732), follow this

procedure Adjust the DC power supply VSS to produce 0 to +11.0 Volts across R1 by monitoring with the DMM1 Measure the forward turn-on voltage of the diode with DMM2 If two DMMs are not available at your lab bench, you may have to switch back and forth between the two terminals at DMM1 and DMM2 Record the diode's current and voltage in a table in your notebook The diode current is equal to ?V/R1 Change the voltage to the next value and repeat After measuring ten different different (I,V) pairs for the diode, change the diode to the next one and repeat each of the ten

measurements again Trade off between lab group members, so that everyone gets to do

at least one diode

Question-2:

Using some graph paper, plot the common (base 10) logarithm of the current versus the voltage for each diode; that is, create a semi-log plot of I versus V, where I is on a log scale and V is on a linear scale

(b) For each decade of increase in diode current, how much does the diode voltage increase by?

Diode voltage increase veryslow but when it meet the jumpoint it will increasing sighly for each decade

(c) Identify current ranges on your graph that correspond to diode ideality factors of

1 and 2 Identify any other obvious trends

For 1N4007 Id run from 1mA to 12mA, 1N5819 is the same with 1N4007 but 1N4731 is in reverse bias with range of Id run from -1mA to -7mA

(d) Rank the four diodes from smallest to largest turn-on voltage How does this ranking compare to that for reverse leakage current?

0 0.1

0

0

0

0.01

0.01

0.01

0.01

-6 -5 -4 -3 -2 -1 0 1 2

-0.01 -0.01 0 0 0 0 0 0.01 0.01 0.01 0.01

1 N4 73 2

Vd

1 : 1N5819, 2 : 1N4007

Obiviously this ranking compare to that for reverse leakage current show the power consumption for each type of diode

Procedure 3 Measurement of diode I-V characteristics using the oscilloscope: Comment In this procedure, you will use an oscilloscope and the laboratory transformer

to display the current-voltage (I-V) characteristics of a diode

Set-Up Connect the circuit shown in Fig E1.3 using the following components: R1 = 1.0 k Ω 1% 1/4 W

D1 = 1N4007

Set-Up Set the signal generator to 10 V amplitude, and 60 Hz frequency Connect the

positive lead from the signal generator and the 10x probe from Ch-1 of the oscilloscope

to the anode of the diode Connet the 10x probe from Ch-2 of the oscilloscope to the junction between D1 and R1 Connect the ground lead from the signal generator and the

two oscilloscope probe grounds to the other side of R1, as shown in Figure E1.3

Next, configure an oscilloscope to display the I-V characteristics as follows: Configure

the oscilloscope to produce an X-Y display, using Ch-1 as the X-axis and Ch-2 as the Y-axis Set Ch-2 to invert the incoming signal Set the Ch-1 range to 0.1 V/div which establishes the x-axis scale of the display as 1.0 V/div, since a 10 Ω probe is being used Set the Ch-2 range to 0.5 V/div which establishes the y-axis of the display to 0.5 mA/div, as a result of the value of R1 = 1.0 k Ω and the 10 Ω probe

Turn ON the power switch to energize the circuit At this point you should have something on the screen which resembles the I-V characteristics of a diode Adjust the position controls to center and calibrate the curve to the center point of the screen as follows: Switch both Ch-1 and Ch-2 input couplings to GND Adjust the vertical position control for Ch-2 and the horizontal position control to move the dot to the exact

center of the oscilloscope screen After having done so, return both the Ch-1 and Ch-2 input couplings to DC You may need to decrease the intensity of the trace to remove any halo from around the dot

Comment: The oscilloscope should now be displaying a graph of the current-voltage

(IV) characteristics of the device The vertical axis or y-input is proportional to the current through the diode, since it measures the voltage across R1 The voltage across R1 is proportional to the current flowing through it, and this same current flows through the diode The horizontal axis or x-input is proportional to the voltage across the diode Thus, this circuit produces a simple, but effective and accurate curve tracer Note that the Ch-2 input to the oscilloscope must be inverted in order to account for the polarity of the voltage drop produced across R1 This then keeps the I-V characteristics of a passive device within quadrants 1 and 3 of the I and V axes, as they are normally drawn

Measurement-3: Sketch the I-V characteristics of each diode in your notebook (they

should look like the oscilloscope trace) on the same set of axes Using the scaling factors from the oscilloscope, scale the x and y axes of your sketch with tick marks for current and voltage Graph paper is handy for this and makes the following analysis easier

Question-3: From your sketch, extract the forward-bias turn-on voltage (Von) for each

diode Compare your answers to the results of the previous DMM readings

Procedure 4 Effect of series and parallel resistances

Comment The set-up from Procedure 3 can be kept as-is, aside from changing the diode

back to the 1N5819 type

Set-Up Use the following parts to construct the circuit of Fig E1.4 below:

R1 = 1.0 k Ω 1% 1/4 W

D1 = 1N5819

Measurement-4 Sketch the I-V characteristics of the 1N5819 diode in your notebook

and label the current and voltage axes with tick marks matching to the scale factors on

the oscilloscope

Now, add another 1.0 k Ω 1/4W resistor in parallel with D1 and observe the effect on the I-V characteristics, as displayed on the oscilloscope screen Sketch these new characteristics in your notebook on the same set of axes as the first I-V curve This new

I-V curve represents how the diode is affected by a parallel leakage path

Next, replace the D1 and 1.0 k Ω parallel combination with D1 and a 100 Ω resistor

in series and observe the effect on the I-V characteristics Sketch these new

characteristics in your notebook on the same set of axes as the other two I-V curves This new I-V curve represents how the diode is affected by additional series resistance which might arise from a poor contact or a faulty connection in a circuit

Question-4 Using only a few well-chosen sentences, discuss the effects of series and

parallel resistance on the observed I-V characteristics of a diode Refer to your sketch of the characteristics as needed

 When connected in series, we observe the following properties to hold true among the diodes:

 Resultant diode’s forward voltage increases.

 Reverse blocking capabilities of diodes are increased in series connection V-I characteristics show that the diodes have different blocking voltages In forward biased state, the voltage drop and the forward current would be same on the diodes While in the reverse biased the blocking voltage is different as the diodes have to carry the same leakage current

This problem can be solved by connected resistances across every diode Voltage would be shared equally; hence the leakage current would differ

 Parallel connection means the components are connected across each other, having two common points Current differs across each component while voltage drop is same When diodes are connected in parallel, this same trend is observed

 Current carrying capacity increases

 No conduction in resultant diode in both sides

Diodes of same type having same voltage drops can be used for steady state conditions In this case, the parallel diodes would have the same reverse blocking voltages Some precautions are to be kept in mind while using the diodes with same forward voltage drops, which are:

 The diodes should have same heat sinks

 They should be cooled equally when necessary

Negligence would change the temperature of the diodes unequally This will in turn cause the forward characteristics to differ which can create problems

Procedure 5 Measurement of a zener diode

Set-Up Connect the circuit shown in Fig E1.5 using the following components: R1 = 1.0 k Ω 1% 1/4 W

D1 = 1N4732

Set-Up Set the signal generator to 5 V amplitude, and 1000 Hz frequency Connect the

positive lead from the signal generator and the 10x probe from Ch-1 of the oscilloscope

to the anode of the diode Connet the 10x probe from Ch-2 of the oscilloscope to the junction between D1 and R1 Connect the ground lead from the signal generator and the

two oscilloscope probe grounds to the other side of R1, as shown in Figure E1.5

Next, configure an oscilloscope to display the I-V characteristics as follows: Configure

the oscilloscope to produce an X-Y display, using Ch-1 as the X-axis and Ch-2 as the Y-axis Set Ch-2 to invert the incoming signal Set the Ch-1 range to 0.1 V/div which establishes the x-axis scale of the display as 1.0 V/div, since a 10 probe is being used  Set the Ch-2 range to 0.5 V/div which establishes the y-axis of the display to 5 mA/div,

as a result of the value of R1 = 1.0 k Ω and the 10 Ω probe

Turn ON the power switch to energize the circuit At this point you should have something on the screen which resembles the I-V characteristics of a diode Adjust the position controls to center and calibrate the curve to the center point of the screen as follows: Switch both Ch-1 and Ch-2 input couplings to GND Adjust the vertical position control for Ch-2 and the horizontal position control to move the dot to the exact center of the oscilloscope screen After having done so, return both the Ch-1 and Ch-2 input couplings to DC You may need to decrease the intensity of the trace to remove any halo from around the dot

Measurement-5: Sketch the I-V characteristics of each diode in your notebook (they

should look like the oscilloscope trace) on the same set of axes Using the scaling factors from the oscilloscope, scale the x and y axes of your sketch with tick marks for current and voltage Graph paper is handy for this and makes the following analysis easier

Question-5

(a) Using the data that was collected, compute a value for the zener resistance rz of the diode in its breakdown region Similarly, compute a value for the forward (on) resistance

rf of the diode in its forward region The easiest way to do this for both regions is to identify two strategic (I,V) points which define the best fit lines in these regions and then compute the inverse slopes of these lines

(b) The power rating of the 1N4732 zener diode is quoted at 1.0 Watt Calculate the maximum current that the diode can handle in the forward (on) direction and then in the reverse (zener) direction and not exceed the 1.0 Watt limit